TypeScript: Support a TS 3.9 breaking change for Optional Chaining and Non-Null Assertions

changelog_unreleased/typescript/pr-8450.md

@@ -0,0 +1,16 @@
+#### Support TypeScript 3.9 breaking change for Optional Chaining and Non-Null Assertions ([#8450](https://github.com/prettier/prettier/pull/8450) by [@sosukesuzuki](https://github.com/sosukesuzuki))
+
+See https://devblogs.microsoft.com/typescript/announcing-typescript-3-9/#breaking-changes
+
+<!-- prettier-ignore -->
+```ts
+// Input
+(a?.b)!.c;
+
+// Prettier stable
+a?.b!.c;
+
+// Prettier master
+(a?.b)!.c;
+
+```

src/language-js/needs-parens.js

@@ -626,6 +626,14 @@ function needsParens(path, options) {
 
     case "OptionalMemberExpression":
     case "OptionalCallExpression":
+      if (
+        node.type === "OptionalMemberExpression" &&
+        parent.type === "TSNonNullExpression" &&
+        path.getParentNode(1).type === "MemberExpression"
+      ) {
+        return true;
+      }
+
       if (
         (parent.type === "MemberExpression" && name === "object") ||
         ((parent.type === "CallExpression" ||

tests/typescript/non-null/__snapshots__/jsfmt.spec.js.snap

@@ -32,6 +32,34 @@ foo!.bar().baz().what();
 ================================================================================
 `;
 
+exports[`optional-chain.ts format 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+a?.b!.c;
+a?.b!.c.d;
+a?.b.c!.d;
+a!.b?.c;
+a?.b!?.c;
+a?.b!.c?.c;
+(a?.b!).c;
+(a?.b)!.c;
+
+=====================================output=====================================
+a?.b!.c;
+a?.b!.c.d;
+a?.b.c!.d;
+a!.b?.c;
+a?.b!?.c;
+a?.b!.c?.c;
+(a?.b)!.c;
+(a?.b)!.c;
+
+================================================================================
+`;
+
 exports[`parens.ts format 1`] = `
 ====================================options=====================================
 parsers: ["typescript"]

tests/typescript/non-null/optional-chain.ts

@@ -0,0 +1,8 @@
+a?.b!.c;
+a?.b!.c.d;
+a?.b.c!.d;
+a!.b?.c;
+a?.b!?.c;
+a?.b!.c?.c;
+(a?.b!).c;
+(a?.b)!.c;